Of the 9 RA sera that only reacted with 1 peptide (Table 2, first column), 22% reacted with the proteoglycan peptide (n = 2), 22% with the fibronectin peptide (n = 2) and 56% (n = 5) with EBNA-2 peptide. The gene discussed is FN1; the disease is rheumatoid arthritis.